1. The Field of the Invention
The present invention relates to an apparatus and method for detecting occlusions and other pressure changes during administration of solutions to a patient. More particularly, the present invention relates to a force sensor for an infusion set which detects occlusions in a tube during administration of a solution to a patient.
2. State of the Art
Treating a patient often requires administering to the patient certain fluids, medication or other nutrients in solution form. The physical condition of a patient may require enteral feeding of a nutrient solution into a patient's stomach or bowel. Likewise, a patient may require parenteral or intravenous infusion of medication, hydration and/or nutrients. Furthermore, there are times when a pressurized solution is provided to a patient to clean out diseased tissue or a wound.
In enteral feeding, it is important to provide the solution within a desired pressure range to ensure the solution, which can be somewhat viscous, is delivered, but at a pressure which is not uncomfortable to the patient or which could damage tissue surrounding the outlet of the feeding set. While controlling pressure is a concern, medical personnel must also be concerned about possible occlusion of the feeding set which prevents delivery of the feeding solution. This can be caused by a blockage within the feeding tube by, for example, materials in the feeding solution, or externally by the feeding set being crimped or otherwise obstructed by the patient or some other cause.
Likewise in parenteral feeding, it is important to deliver the solution to the patient as the patient may require the medication, fluids or nutrition in the infused solution in order to survive. As with enteral feeding, the infusion of solutions parenterally should be done at a pressure low enough to avoid damage to the veins while at sufficient pressure to assure delivery of the solution. Likewise, it is also important to ensure that flow of the solution has not been occluded.
Other situations which require delivery of solutions have similar concerns. For example, irrigation of wounds to remove bacteria and foreign material is an essential of wound management. Conventional methods of irrigating a wound include gravity flow and bulb syringe procedures. However, considerable practice variation exists in the details of technique. An important factor in wound irrigation is volume; increased volume improves wound cleansing to a point, but the optimal volume is unknown. Additionally, high-pressure flow has been shown to remove more bacteria and debris and to lower the rate of wound infection compared with low-pressure irrigation, but high-pressure flow may lead to increased wound trauma which, in turn, increases the time for a wound to heal. Similarly, antiseptic additives can kill bacteria in the wound, but host-tissue toxicities may limit their use.
According to principles of the present invention, to overcome the inherent variability of conventional wound irrigating procedures, solutions can be administered to the patient using an infusion pump. Administering solutions to patients using an infusion pump is well known in the medical arts. Infusion pumps are often used to deliver fluids, medications or nutrients from a reservoir to the patient via tubing. The use of an infusion pump allows for the continuous or periodic delivery of these solutions to the patient without the need of constant supervision by medical personnel. Moreover, infusion sets that utilize a pump, or some other apparatus to apply a positive force to the solution in the tubing to facilitate flow, can more precisely control the rate and timing of delivery. With controlled infusion using an infusion pump, the solution can be delivered at a precise rate that will keep the solution's concentration within the therapeutic margin and out of any potentially cytotoxic range.
While the use of an infusion pump to deliver medications and other solutions has the advantages described above, there is a risk that flow of a solution through the tubing may become impeded, resulting in the patient not receiving needed fluids and medications. For example, a patient may unintentionally roll onto the tubing thereby compressing the tubing and stopping or reducing the flow, or, a blood clot or other debris may block the flow of solution through the tubing. To overcome these types of problems standard safety features on modern infusion pumps include a downstream sensor to detect changes in flow of a solution through the tubing and to warn medical personnel when the tubing is impeded.
Furthermore, it has been found that irrigating wounds at pressures below 4 pounds per square inch (psi) may not adequately cleanse the wound. Thus, for example, more optimum irrigation pressures may be between 6-14 psi and may preferably be about 8-12 psi to be more effective at cleansing the wound and reducing wound trauma and wound infection. Therefore, it is desirable to have a sensor that is capable of detecting a change in pressure within the tubing in these ranges when using an infusion pump to deliver solutions to a patient's wound.
Thus, there is a need for a sensor that produces a signal that is easily discernable between atmospheric pressure and a desired in-line tubing pressure (e.g. 4 psi, 8 psi, 10 psi, etc.) to allow for the continuous and precise delivery of solutions during enteral feeding, parenteral solution infusion, wound irrigation, or the like to improve delivery. It is also desirable to provide such a device which is relatively inexpensive and easy to use.